1. Field of the Invention
The present invention relates to a power interconnection system, and more particularly to a power interconnection system for providing a low impedance connection between a chip package, such as a CPU chip, and a voltage regulator circuit.
2. Background of the Invention
Modern CPU chips require output of high current at relatively low voltage levels, typically in the range of zero to five volts. Although the CPU chip requires high current, the current demands for the requirements of the CPU chip typically fluctuate widely. For example, in the sleep or idle mode, a CPU chip might require currents varying in the range of 0.5 A to 5 A, while a CPU chip running in a faster computing mode might require currents ranging from 10 A to 100 A. However, even though current requirements for the CPU chip fluctuate widely, the voltage limits required by the CPU chip needs to remain relatively stable no matter what operation mode the CPU chip is running at.
Requirements for tight voltage regulation in response to highly variable current demands indicate that the main power supply output can no longer be fed directly to the CPU chip. Instead, a voltage regulator is utilized to deliver a tightly controlled voltage to the CPU chip. As such, a local voltage regulator can supply a high level of DC current along with minimization of the uncertainty in voltage drops between the main power supply and the CPU chip.
Suggestion exists that the voltage regulator should be placed in close proximity to the CPU chip. That is because if the voltage regulator is spaced far away from the CPU chip, impedance between the voltage regulator and the CPU chip increases with the spaced distance, thereby causing poor voltage regulation generated at the CPU chip. Furthermore, an increase in impedance will result in the decreases of speed and power delivery. As the current CPU chip tends to focus on the speed-increasing requirement as well as the effective power delivery, the increase in impedance will become less and less acceptable.
A problem with positioning the voltage regulator in close proximity to the CPU chip on a common printed circuit board is that some periphery devices may need to work with the CPU chip much more. For example, a heat sink for use with the CPU chip needs to be directly disposed above the CPU chip by its heat sink retention member fastened to the specific region peripheral to the CPU chip. Further, a few memory chips or integrated circuits also need to be close to the CPU chip for reasons of signal integrity. Therefore, in the existing power interconnection configuration, the voltage regulator is located more far away from the CPU chip, since the above periphery devices have occupied the limited board space close to the CPU chip. Obviously, as stated above, this will result in the increase of impedance and the decrease of the power delivery.